This invention relates to a medication infusion device having a finger type pump unit wherein three or more fingers are moved in a predetermined sequence, and wherein a feeding tube for medication is placed between a cap and said fingers, and squeezed by said fingers to infuse the medication into the human body.
An infusion device of the type described has been proposed for infusion of a small amount of medication such as insulin. For example, in the treatment of a diabetic patient, it is necessary that insulin be continuously and cyclically infused into the body of the patient. Since the insulin requirement of a patient is subject to substantial fluctuations caused by the meal cycle, sleep or energy consumption as when the patient walks, a small-sized portable insulin infusion device has been proposed in which prescribed infusion doses are preset for certain times so that cyclic insulin infusion may be made in accordance with the insulin requirements of the body that change with time. The infusion device defined above may be applied to the proposed insulin infusion device.
The insulin infusion device has a memory in which the amount of liquid infused per unit time may be programmed on the basis of the presumed physical condition and behavior of the patient over a twenty-four hour period. The device also has a clock generator for generating clock pulsed for calling data from memory at predetermined time intervals, and a motor drive circuit for rotating a motor a certain number of revolutions conforming to the data called forth from the memory by the clock. The pump unit and the pump control unit may be enclosed in respective casings. The pump unit acts to dispense the liquid by squeezing or collapsing the feeding tube of a disposable insulin vessel and may operate for a required time interval such as one minute, as instructed by the pump control unit for dispensing the required insulin dose programmed in the memory.
The infusion device of this kind may be applied not only to the infusion of insulin but also to any repeated and continued infusion treatment in which liquid medication is administered in equal or differing doses per time unit.
The prior-art pump does not lend itself to a reduction in size easily because of the large number of components and numerous assembly steps. Moreover, a small-sized pump exhibits disminished durability, while the amount of dispensed liquid cannot be adjusted minutely without considerable difficulties. Thus it is not easy to obtain an infusion device by using a small sized version of the prior-art pump.
FIG. 1 shows a prior-art finger type pump unit including a feeding tube C, fingers 1, finger guides 2, cams 3, a cam shaft 4, coil springs 5, a cap 6 and a casing 7. Liquid may be dispensed by sequential actuation, in the liquid feed direction, of the fingers which are capable of squeezing the tube C. At least three fingers 1 are required in this case, but a larger number of fingers 1 are required to dispense the liquid smoothly. The number of cams 3 and coil springs 5 required is the same as the number of the fingers 1. A large number of components and manufacturing steps are required and space must be provided for housing and assembly of these components, thus making it difficult to reduce the size of the pump unit and infusion divice. Furthermore, adjustment of the amount of liquid dispensed per revolution of the cam shaft of the finger-type pump unit is practically impossible due to structural limitation. Also, loss of electrical power due to friction between a multiplicity of fingers and finger guides cannot be neglected in view of the limited power supply of the portable type infusion device.